This invention relates generally to wind turbines, and more particularly to methods and apparatus for controlling wind turbine actuation to compensate for variations in wind speed.
Recently, wind turbines have received increased attention as environmentally safe and relatively inexpensive alternative energy sources. With this growing interest, considerable efforts have been made to develop wind turbines that are reliable and efficient.
Generally, a wind turbine includes a rotor having multiple blades. The rotor is mounted to a housing or nacelle, which is positioned on top of a truss or tubular tower. Utility scale grade wind turbines (i.e., wind turbines designed to provide electrical power to a utility grid) can have large rotors (e.g., 70 or more meters in diameter). Blades on these rotors transform wind energy into a rotational torque or force that drives one or more generators that may be rotationally coupled to the rotor through a gearbox. The gearbox steps up the inherently low rotational speed of the turbine rotor for the generator to efficiently convert mechanical energy to electrical energy, which is fed into a utility grid in some known embodiments.
The most significant source of variations in the operation of a wind turbine is the variation in the wind speed that acts on the rotor. An efficient utilization of controlled actuation to compensate for such variations in wind speed depends on prompt measurement or estimation of such variations. Lags and delays on the estimation of the effective wind speed lead to reduced efficacy in energy capture and tower fatigue reduction.
Some known techniques for estimating wind speed are based on measurements of rotor speed, blade pitch angle and generator torque/electrical power. Other known techniques for estimating wind speed use tower position information that offers improvements in response time over generator torque measurements techniques. Yet other known techniques employ measurement systems such as Lidar to obtain the effective average wind speed ahead of the turbine. Still another known technique uses strain measurements of piezoresistive cement-based materials in a 4-pole electrode arrangement. While the foregoing solutions are very effective, the cost of those measurement systems is still much too high and economically disadvantageous. Further, the use of adhesives, cements and/or bonding agents is generally highly sensitive to the electrode-tower contact and is therefore not optimal for large numbers of measurement points over a large area of a wind tower.
In view of the foregoing, it would be advantageous to provide methods and apparatus for controlling wind turbine actuation faster, more reliably, and in a more cost effective manner than that which is achievable using known techniques that compensate for variations in wind speed.